1. Technical Field
The present invention relates to an optical filter, an analytical instrument, an optical apparatus, and so on using the optical filter.
2. Related Art
An interference filter has been proposed that has a variable transmission wavelength (see JP-A-11-142752). As shown in FIG. 3 of JP-A-11-142752, a pair of substrates are held parallel to each other, a pair of multilayer films (reflecting films) are formed on the pair of substrates so as to be opposed to each other with a gap having a constant distance therebetween, and a pair of electrostatic drive electrodes are provided for controlling the gap. Such a variable wavelength interference filter generates electrostatic attractive force in accordance with a voltage applied to the electrostatic drive electrodes to control the gap, thereby making it possible to vary the center wavelength of a transmission light beam.
A requirement for such variable wavelength interference filters is to control the gap between the pair of reflecting films with good accuracy using an electrostatic actuator. Since the target is the wavelength of light, nanometer gap accuracy is required. In particular, a variable wavelength filter that makes it possible to perform wavelength selection in a wide band requires highly accurate gap control with a fine displacement within a limited drive voltage range while achieving large gap displacement (movable range).